Replace crankset only or BB as well?

[marcinski]

Hi,

I am new to this forum so please bear with my silly questions.

I have a Trek FX 7.0 wich I really like despite the fact that it has cheap and nasty parts. I've got 14-28 7-speed freewheel which I recently replaced having worn the oryginal one. It's got cheap looking and a bit rusty 28-38-48 triple in the front. I found myself riding on the higher gear mostly, i.e. big chainring on the front and 5th to 7th sprocket on the rear. For that reason I am considering the upgrade to something like 30-42-52 or similar crankset. this would give me an extra high gear without compromising much on the low end.
Noe the question is, Should I replace the crankset only (square taper fit) ar should I go ahead and change the BB to something better as well?Current BB seems fine although the spindle is quite a bit rusty.

Any advice appreciated,

Thanks,

Marcin

 

[Cranks]

Let a bike shop or someone experienced look at your bb, if the condition is ok then leave it.
However, the new chainset may force you to replace the bb as the axle length on your bb may not be compatible.

 

[MacB]

if the frame's ok then upgrading as parts wear out seems to be a very acceptable way of progressing. Just need to keep an eye on compatibility etc.

I don't get the impression that frame quality varies much until you get to top end of a range. If you do the maths on a bike build, I know the economies of scale avaliable to the biggies are huge, there isn't a big allowance for frame.

 

[marcinski]

Thank you for the replies. I don't think there is anything wrong with BB at the moment (well apart from the rusty spindle, but I geuss it's harmless). I was just wandering if it's worth to upgrade to a newer type of BB, like Hollowtech II, or should I just stick to what I have and replace it when it's worn.
BTW, I thought that's only the axle length that determines the chain line, so any crankset that I fit should give me the same chain line, is it right?

thanks,

Marcin

 

[Cranks]

You're right in that the bb will effect the chainline, however, chainsets have different spider depths so that will matter too.
Pain in the a£$e eh!
When you buy the chainset, take a look at the instructions which will recommend a bb axle length.

 

[marcinski]

Oh, I see, thanks a lot.